Peroxy compounds and vulcanizable compositions thereof

ABSTRACT

A novel class of compounds having the formula ##STR1## where Z is a substituted carbonate or carbamate, D is alkynyl or an alkyl, and the R&#39;s may be alkyl.

This is a division of application Ser. No. 937,657, filed Aug. 28, 1978,now U.S. Pat. No. 4,180,518 issued Dec. 15, 1979.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel compounds having both a peroxy group anda substituted hydroxy group attached to a backbone chain of at least 4carbons. These novel compounds are especially useful as agents for thecrosslinking or vulcanizing polymers. This invention also relates tovulcanizable compounds of these novel compounds and to an improvedmethod of making a crosslinked or vulcanized material using the novelperoxy compounds as a crosslinking agent.

2. Description of the Prior Art

U.S. Pat. No. 3,236,872 (Manly et al) discloses hexylene glycolhydroperoxides and certain alkyl and ester derivatives thereof havingthe formula ##STR2## where R and R' are hydrogen, acyl, aroyl or alkylgroups. These compounds are also disclosed as crosslinking agents. Manlyet al is completely silent on the preparation of carbonate or carbamatederivatives of the so-called hexylene glycol peroxides shown by theformula supra.

SUMMARY OF THE INVENTION

The novel class of peroxides of this invention have the followinggeneral structure: ##STR3## where: (a) R₁ is hydrogen or an alkyl of 1-4carbons

(b) R₂ and R₃ are independently an alkyl of 1 to 8 carbons;

(c) R₄ is t-alkyl of 4-10 carbons, t-aralkyl of 9-16 carbons,t-cycloalkyl of 6-12 carbons, ##STR4## (e) R₅ and R₇ are independentlyan alkyl of 1-8 carbons, a cycloalkyl of 5 to 11 carbons, an aralkyl of7-18 carbons or an aryl having one or more benzene nuclei which may befused or condensed.

(f) R₆ and R₈ are independently hydrogen, alkyl of 1-8 carbons,cycloalkyl of 5 or 6 carbons, phenyl or alkylphenyl of 7-10 carbons; and

(g) D is an alkynyl or alkyl having 1-8 carbons.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that certain new derivatives of1,3-dimethyl-3-hydroperoxybutyl alcohol (hexylene glycol hydroperoxide)or 1,3-dimethyl-3-(t-butylperoxy)butyl alcohol (hexylene glycol t-butylperoxide), namely the carbonate or carbamate derivatives, have speciallyefficacious properties as crosslinking or vulcanizing agents whencompared to the prior art compounds. In other words, Applicants havesurprisingly found that their carbonate and carbamate derivatives have abetter crosslinking efficiency than the prior art compounds; thecarbonate and carbamate derivatives give crosslinking efficiencies of85% or better at 10 milliequivalents for 100 parts of polymeric compoundwhereas the carboxylate derivatives covered in the prior art give ingeneral polyethylene (PE) crosslinking efficiencies at or below 80%.

COMPOUNDS I

In the compound ##STR5## the backbone structure ##STR6## has at least 4carbons; the backbone may have up to 22 carbons but commonly has 5-18carbons. At least one carbon separates the tertiary carbon ##STR7## towhich the peroxy group is joined from the carbon ##STR8## to which thecarbonate or carbamate radical is joined. D is an alkynyl of 2-8 carbonsor an alkyl of 1-8 carbons which may be straight or branched chain.

R₁ is either a hydrogen or an alkyl of 1-4 carbons such as methyl,propyl or butyl.

R₂ and R₃ are independently an alkyl of 1 to 8 carbons, but preferablyof 1 to 4 carbons such as methyl, ethyl or butyl group.

R₄ is a tertiary alkyl radical of 4-10 carbons with a preferred range of4-8 carbons. R₄ may be tertiary aralkyl of 9-15 carbons or tertiarycycloalkyl of 6-10 carbons. R₄ may also be ##STR9## where R₇ is an alkylof 1-8 carbons, a cycloalkyl of 5-11 carbons, an aralkyl of 7-18 carbonsor an aryl having one or more benzene nuclei which may be fused orcondensed. R₆ and R₈ are independently hydrogen, alkyl of 1-8 carbons,cycloalkyl of 5 or 6 carbons, phenyl or alkylphenyl of 7-10 carbons.

Z is either ##STR10## where R₅ has the same definition as R₇ but isindependent thereof. R₆ and R₈ have been defined supra.

Typical peroxy compounds of the invention are:

1. 1,3-Dimethyl-3-(ethoxycarbonylperoxy)butyl ethyl carbonate.

2. 1,3-Dimethyl-3-(t-butylperoxy)butyl n-butyl carbonate.

3. 1,3-Dimethyl-3-(t-butylperoxy)butyl N,N-dimethylcarbamate.

4. 1,3,Dimethyl-3-(t-butylperoxy)butyl N-methylcarbamate.

5. 1,3-Dimethyl-3-(t-butylperoxy)butyl carbamate.

6. 1,3-Dimethyl-3-(N-cyclohexylcarbamoylperoxy)butylN-cyclohexylcarbamate.

7. 1,3-Dimethyl-3-(N,N-dimethylcarbamoylperoxy)butylN,N-dimethylcarbamate.

8. 4-Methyl-4-(t-butylperoxy)pentyl N,N-dimethylcarbamate.

9. 4-Methyl-4-(isoproxycarbonylperoxy)pentyl isopropyl carbonate.

10. 1,4-Dimethyl-4-(t-butylperoxy)pentyl isopropyl carbonate.

11. 1,3,3,5-Tetramethyl-5-(N,N-dimethylcarbamoylperoxy)hexylN,N-dimethylcarbamate.

12. 1-(Ethoxycarbonyloxy)-4-(t-butylperoxy)-4-methylpent-2-yne,otherwise named 4-Methyl-4-(t-butylperoxy)pent-2-ynyl ethyl carbonate.

13.1-(N,N-dimethylcarbamoyloxy)-4-(N,N-dimethylcarbamoyl-peroxy)-4-methyl-pent-2-yne,otherwise named 4-methyl-4-(N,N-dimethylcarbamoylperoxy)-pent-2-ynylN,N-dimethylcarbamate.

14. 3,7-Dimethyl-7-(t-butylperoxy)octyl N,N-dimethylcarbamate.

15. 3,7-Dimethyl-7-(t-butylperoxy)octyl n-butyl carbonate.

16.2-[N-(4-Methylphenyl)carbamoyloxy]-4-n-butyl-4-(α,α-dimethylbenzylperoxy)octane.

17.2-(2-Ethylhexoxycarbonyloxy)-7-methyl-7-(α,α-dimethyl-4-phenylbenzylperoxy)octa-3,5-diyne.

18. 1-(N,N-Di-n-butylcarbamoyloxy)-9-methyl-9-(2-pinanylperoxy)decane.

19.2-(N-Cyclopentylcarbamoyloxy)-4-methyl-4-(1,1,3,3-tetramethylbutylperoxy)pentane.

In general, the compounds I are prepared by the reaction of a glycol (ordiol) with a hydroperoxide. The glycol may be a primary-tertiary or asecondary-tertiary compound. Examples of the glycol are:

(1) Hexylene glycol(1,3-dimethyl-3-hydroxybutyl alcohol),

(2) 3,7-Dimethyl-7-hydroxyoctyl alcohol,

(3) 4-Methyl-4-hydroxypentyl alcohol,

(4) 1,4-Dimethyl-4-hydroxypentyl alcohol,

(5) 1,3,3,5-Tetramethyl-5-hydroxyhexyl alcohol,

(6) 4-Methyl-4-hydroxypent-2-ynyl alcohol,

(7) 2,4-dihydroxy-2-methyloctane,

(8) 2,4-dihydroxy-4-methyloctane,

(9) 2,4-dihydroxy-4-n-butyloctane,

(10) 9-hydroxy-9-methyldecanol, and

(11) 2,7-dihydroxy-2-methylocta-3,5-diyne.

The hydroperoxide reactant may be t-alkyl, t-aralkyl, t-cycloalkyl, ort-alkynyl. Examples of this reactant are the t-butyl, t-amyl,1,1,3,3-tetramethylbutyl, α-cumyl, β-isopropyl-α-cumyl, β-menthyl,pinanyl, 1-methyl-cyclohexyl, or the 1,1-dimethylprop-2-ynylhydroperoxide.

Compounds I are useful as initiators for vinyl polymerization, flameretardant synergists for polystyrene, free radical catalysts, andintermediates in organic synthesis. These compounds are effectivecrosslinking agents for polymers and especially effective forpolyolefins and elastomers.

Compounds I can be positioned on a support carrier when the ultimate usemakes such a composition of desirable; for example, in rubbercompounding, any solid which does not react with the peroxy compound maybe used as a carrier. Suitable carriers are silicates, clays, talc,magnesium carbonate and carbon blacks. The silicates and magnesiumcarbonate are especially preferred carriers.

Compounds I are especially effective crosslinking (vulcanizing) agentsfor polymeric compounds which are capable of being crosslinked to form athermoset material. The compound should be intimately mixed with thepolymeric compound in a sufficient amount to afford the desired degreeof crosslinking. (Note that the words of art, "vulcanizing" and"crosslinking", are used as synonyms).

THE POLYMERIC COMPOUNDS

The polymeric compounds include any of those natural and syntheticmaterials which are thermoplastic or have indefinite melting points andwhich can be transformed to thermoset materials (elastic, or somewhatrigid solids) by a crosslinking reaction, especially through the actionof an added agent. Examples are the polymeric compounds produced by thevulcanizing of natural and synthetic rubber by means of sulfur or peroxycompounds.

Polymeric compounds, that illustrate this invention, are as follows:

(1) Solid polyolefins wherein the preferred ones are polyethylene andpolybutenes.

(2) Elastomers such as natural rubber.

(3) Synthetic rubbers such as butyl rubbers, styrene-butadiene (GR-S)rubber, neoprene, acrylic rubber, Buna rubber, ethylenepropylene rubber(copolymer and terpolymer), polyurethane rubbers, nitrile rubbers andthe silicone rubbers.

(4) Vinyl polymers such as polyvinyl chloride (PVC), polyvinyl acetate(PVAC), PVC-PVAC copolymers, ethylene-vinyl acetate copolymer and thevinyl pyrrolidone polymers and copolymers.

(5) Miscellaneous "elastomers" such as polybutene-styrene copolymers,ethylene and/or propylene-styrene copolymers andacrylonitrile-butadiene-styrene (ABS) copolymers

(6) Various polyether resins, polyester resins, polyamide resins andnatural gums.

The solid polyolefins and elastomers are especially suitable polymericcompounds. The polymers may include plasticizers and/or oil extenders.

VULCANIZABLE COMPOUNDS

It has been discovered that an intimate mixture of the defined polymerand the defined peroxy agent can be heat-cured in reasonable times atreasonable temperatures to a crosslinked (vulcanized) material. Thetemperature and time are controlled to obtain the desired degree ofcrosslinking. Sufficient agent is present to afford the desired degreeof crosslinking.

The peroxy compounds of the invention can be used alone or inconjunction with a coagent or coupling agent--just as the presentlyknown vulcanizing agents are used. Suitable coagents are: sulfur,viscous polybutadiene resins such as Enjay Buton 150, ethylenedimethacrylate, maleic acid, vinyl silane, N,4-dinitroso-N-methylanilineand hexachlorocyclopentadiene.

In addition to the defined polymeric compound and defined peroxycompound in intimate mixture, the vulcanizable composition may includecoagents, promoters, coupling agents, fillers, reinforcing materials,and any other material conventionally used in the production ofvulcanized compositions. Desirable fillers are carbon black, titaniumdioxide, calcium silicate and the alkaline earth metal carbonates. Apreferred filler is the alkaline carbon blacks.

Examples of the novel mix (as parts by weight per 100 parts by weight ofpolymeric compound) are:

MIXTURE A includes

(a) 100 parts by weight of EPR (an ethylene-propylene copolymer),

(b) 1-5 PHR of a peroxy compound of the invention,

(c) 0.1-0.5 parts of a coagent such as sulfur, and

(d) 50-60 parts carbon black.

MIXTURE B includes

(a) low density polyethylene and

(b) about 1-5 PHR of a peroxy compound of the invention.

MIXTURE C includes

(a) low density polyethylene,

(b) about 40-50 PHR of carbon black filler, and

(c) about 1-5 PHR of a peroxy compound of the invention.

MIXTURE D (a polyurethane rubber mixture) includes

(a) 100 parts of Genthane-S-polyurethane rubber,

(b) 25 PHR of carbon black, and

(c) 1-5 PHR of a peroxy compound of the invention. It must be noted thatoil extended EPR can be used in formulations; such a blend consists of100 parts by weight of EPR and 40 parts by weight of mineral oil. Thisblend has a specific gravity of 0.86, a Mooney viscosity (8 ml./212° F.)of 40 and an ash content of 0.6 weight percent.

The vulcanizable composition has the solid polymeric compound,crosslinking agent and other materials in the formulation present in theform of an intimate mixture. The formulation components are milledtogether until a suitable mixture has been obtained. Elevatedtemperatures may be used to assist in the mixing. The mixingtemperatures and time should be controlled with these defined peroxycompounds in order to avoid premature curing or localized curing. In thecase of elastomers, for example, the Banbury mixers may reach a workingtemperature of 250°-260° F. Hence, the vulcanizable composition shouldhave a cure time at these temperatures which permits good mixing withoutthe premature cure, known as scorching in the rubber industry.

The defined peroxy compounds are present in the vulcanizablecompositions of the invention in an amount sufficient to afford thedesired degree of crosslinking. The amount needed is dependent on thetype of polymeric compound present and the types and amounts of coagentand promoters present. In general 0.01 gram-equivalent of a peroxidewill cure 100 grams of EPR (for a monofunctional peroxide the equivalentweight is equal to the molecular weight). Different end uses, however,will require more or less crosslinks (frequently an excess of 25 to 100%is used).

In industry the terminology PHR (parts per hundred parts of polymer orresin) is commonly used in stating formulations. The peroxy compounds ofthis invention are generally present in a vulcanizable composition in anamount comprising about 1-5 PHR.

VULCANIZED COMPOSITIONS

The vulcanizable composition is heat cured for a time sufficient toobtain the desired degree of crosslinking. The heat curing has atemperature-time relationship which is primarily dependent on thepolymeric compound and the peroxy agent present; the heat curing is alsoaffected by the formulation as a whole. It is customary to use a timeequal to about 6-8 half-lives of the peroxy agent.

In the case of elastomers, the vulcanizing may be carried out at atemperature of about 270°-600° F. The cure time is inversely related totemperature. The curing temperature can range from about 270° to 400° F.and the curing time can vary from about 1 minute to 240 minutes (4hours). At the higher temperatures the shorter times are used keeping inmind that the heating cycle for each peroxide should be such that theperoxide undergoes a time-temperature profile of 6 to 8 half-lives. Thedefined peroxy agents give acceptable cure times at the lowertemperatures; this is advantageous to producers because lowertemperatures reduce the possibility of "burning" and the shorter timespermit a greater output on a given piece of equipment. In the case ofpolyolefin and elastomer formulations, the preferred peroxy agents heatcure at a temperature-time relationship of about 300°-340° F. and about10-30 minutes (the longer times are associated with the lowertemperatures). Using somewhat longer times without significant change inthe quality of the product has been observed.

The heat cured (vulcanized) product may develop better physicalproperties on maturing at ordinary temperatures. In the case ofelastomers such a period seems desirable; a 16-24 hour maturing periodis sufficient.

The heat curing may be carried out in any of the manners now used in thepolymer compounding and rubber compounding art. These may be mold cures,oil cures where oil does not harm the polymeric compound, oven cures,steam cures or hot metal bath cures.

EXAMPLES PREPARATION OF THE COMPOUNDS OF THE INVENTION Example I1,3-Dimethyl-3-(t-butylperoxy)butyl n-butyl carbonate (C-I)

To a solution of 8.1 g. (0.11 mole) of n-butyl alcohol and 7.9 g. (0.1mole) of pyridine in diethyl ether cooled to 10°±1° C. was added asolution of 27.0 g. (0.1 mole) 1,3-dimethyl-3-(t-butylperoxy)butylchloroformate. The reaction temperature was controlled at 15°±1° C.during the addition.

After the addition was complete the reaction mixture was allowed to stirfor 2 hours at 20°±1° C. The reaction mixture was then diluted withwater and the organic phase was separated, washed with a 10% aqueoussolution of tartaric acid and water to neutrality.

The organic phase was then dried over anhydrous magnesium sulfate,filtered and the solvent removed under reduced pressure.

After further purification by column chromatography 24 g. of a viscousliquid was obtained. It was identified by means of Infraredspectroscopy.

EXAMPLE II 1,3-Dimethyl-3-(ethoxycarbonylperoxy)butyl ethyl carbonate(C-II)

To a solution of 24.4 g. (0.0786 mole) of (86.4%)1,3-dimethyl-3(ethoxycarbonylperoxy)butyl chloroformate in 100 ml ofdiethyl ether, cooled at 10°±1° C. was added a solution of 4.6 g (0.1mole) of ethanol and 7.9 g. (0.1 mole) of pyridine in 25 ml of diethylether over a period of 20 minutes.

After the addition was completed the reaction mixture was allowed tostir for four hours while the reaction temperature was allowed to riseto 22°±1° C.

The pyridine hydrochloride was filtered off and the organic phase waswashed with 10% solution of tartaric acid and water to neutrality, thendried over anhydrous magnesium sulfate, filtered and the solventevaporated under reduced pressure. A liquid weighing 18.7 g. wasrecovered. The recovered product assayed 87.4% by active oxygen assay.

EXAMPLE III 1,3-Dimethyl-3-(t-butylperoxy)butyl N-methylcarbamate(C-III)

A solution of 105 g. (0.5 mole) 90% 1,3-Dimethyl-3-t butylperoxy)butylalcohol in 150 ml of cyclohexane was placed in a reactor equipped with amagnetic stirrer, a condenser protected by a calcium chloride dryingtube and a thermometer. To the above was added 43 g. methyl isocyanate(50% excess--28.5 g. (0.5 mole) theoretically needed).

An additional 50 ml of cyclohexane and a few crystals of Dabco* werethen added. The reaction mixture was heated to 60° C. over a period ofabout one hour and allowed to stir at this temperature for 4 hours. Thereaction mixture was then allowed to cool to room temperature and stirovernight.

The reaction mixture was stripped of volatile material under vacuum and100 ml of cyclohexane added to the residue. This solution was thenwashed with water to remove the Dabco catalyst, and also with a 40%aqueous ammonium sulfate solution. After drying over anhydrous sodiumsulfate, the cyclohexane was removed under vacuum and a yield of 131.9g. was obtained. The product was identified by infrared techniques.

EXAMPLE IV 1,3-Dimethyl-3-(t-butylperoxy)butyl N,N-dimethylcarbamate(C-IV)

To a solution of (97%) 1,3-dimethyl-3(t-butylperoxy)butyl chloroformate5.2 g. (0.02 mole) in diethyl ether, cooled to 0°±1° C. was added asolution of dimethylamine, 1.8 g. (0.04 mole) in diethyl ether over aperiod of 10 minutes. After the addition was complete the mixture wasallowed to stir for two hours while the reaction temperature was allowedto rise to 20°±1° C. The reaction mixture was then filtered to removethe amine hydrochloride and the organic phase washed with 10% aqueousTartaric acid solution and water to neutrality.

The ethereal phase was dried over magnesium sulfate, filtered and thesolvent evaporated under vacuum. A yield of 5.1 grams of a colorlessliquid was obtained which was identified by infrared spectroscopy.

EXAMPLE V 1,3-Dimethyl-3-(N-cyclohexyl-carbamoylperoxy)butylN-cyclohexylcarbamate (C-V)

A mixture of 18.7 g. (0.15 mole) of cyclohexyl isocyanate, 6.7 g. (0.05mole) of 1,3-dimethyl-3-hydroperoxybutyl alcohol and 3 drops oftriethylamine was stirred for five days at ambient temperature. Thereaction vessel was protected with a calcium chloride tube to keep outmoisture. Within two days, a solid began to appear, and after the fiveday stirring period the reaction mixture was stripped in vacuo. Theresidue was slurried in 100 ml of ether and filtered. The filter cakewas washed with an additional 30 ml of ether and air dried. A total of7.5 grams of a colorless solid was obtained.

The solid was taken up in 150 ml of boiling ether and then filtered. Theresidue weighed 1.5 grams and melted at 224°-226° C. and was identifiedas N,N'-dicyclohexiurea.

The ethereal filtrate was concentrated and cooled to 0° C. and acolorless solid separated. A total of 4.6 g. of the desired product witha melting point of 115°-117° C., assaying 99% based on active oxygencontent was obtained.

EXAMPLE VI 1,3-Dimethyl-3-(t-butylperoxy)butyl isopropyl carbonate(C-VI)

A four-necked 500 ml. round-bottomed flask was equipped with amechanical stirrer, reflux condenser surmounted by calcium chloridedrying tube, addition funnel and thermometer. A solution of 19 g. (0.1mole) 1,3-dimethyl-3-(t-butylperoxy)butyl alcohol and 13.3 g (slightlyover 0.1 mole) quinoline in 250 ml. pentane was placed in the flaskwhich was placed in a water bath at 221/2° C. Then 12.3 g (0.1 mole)isopropyl chloroformate was added dropwise over 5 minutes; thetemperature did not rise over 23° C. Reaction was not complete after 3days. Another 3 g. of quinoline was added, and the reaction wascompleted after another 3 days as indicated by the fact that no furtherprecipitate of quinoline hydrochloride formed when an aliquot of cleanpentane solution was withdrawn from the reaction mixture and allowed tostand for 15 minutes. The quinoline hydrochloride was filtered off andwashed with 25 ml pentane which was added to the pentane solution. Thissolution was then successively washed with 25 ml. of 7% hydrochloricacid, two 50 ml. portions of water, and finally dried over sodiumsulfate. After removal of drying agent and pentane, a yield of 23.8 g.(86.4%) of material found to be 1,3-dimethyl-3-(t-butylperoxy)butylisopropyl carbonate by infrared analysis, was obtained.

EXAMPLE VII 3,7-Dimethyl-7-(t-butylperoxy)octyl n-butyl carbonate(C-VII)

To a solution of 7.9 g (0.03 mole) of 3,7-dimethyl-7(t-butylperoxy)octylalcohol and 2.4 g (0.03 mole) of pyridine in diethyl ether cooled at10°±1° C. was added a solution of 4.09 (0.03 mole) of n-butylchloroformate in diethyl ether. The reaction temperature was maintainedat 15°±1° C. during the addition.

The reaction mixture was allowed to react for two hours at 20°±1° C. Thereaction mixture was diluted with water and the organic phase separated,washed with 10% aqueous solution of tartaric acid and water toneutrality.

The ethereal solution was dried over anhydrous magnesium sulfate,filtered and the solvent removed under reduced pressure. A colorlessliquid weighing 8 g was obtained. It was identified by means of InfraredSpectroscopy.

The above-mentioned starting reactant,3,7-dimethyl-7-(t-butylperoxy)octyl alcohol, was prepared by firstreacting, 3,7-dimethyl-7-hydroxy octyl alcohol with hydrogen peroxide toform 3,7-dimethyl-7-(hydroperoxy)octyl alcohol which was then alkylatedwith t-butyl alcohol to give said starting reactant.

EXAMPLES VIII to XII Preparations of Additional1,3-Dimethyl-3-(t-Butylperoxy)butyl Alcohol Derivatives

Table A summarizes yields, assays and other synthetic data on severaladditional 1,3-dimethyl-3-(t-butylperoxy)butyl alcohol derivatives. Thefollowing general procedure was employed for their preparations:

One equivalent of 1,3-dimethyl-3-(t-butylperoxy)butyl chloroformate wasslowly added to one equivalent of reactant (see Table A), dissolved in asolvent inert to the reaction such as pentane, benzene, diethyl ether,etc., in the presence of a base (see Table A) at 0° C. to about 50° C.After a 2 to 4 hour period of stirring, the resulting mixture was pouredinto water, additional organic solvent was added and the organic phasewas separated from the aqueous phase. The organic phase was then washedwith aqueous dilute mineral acid solution, then with aqueous base, andfinally with water to neutral. After drying over anhydrous MgSO₄ thefiltered solution was stripped of solvent in vacuo leaving the desiredproduct.

                                      Table A                                     __________________________________________________________________________    Additional Derivatives of 1,3-Dimethyl-                                       3-(t-Butylperoxy)butyl Alcohol                                                Reactant.sup.1  Base      Product        Assay, %                                                                           Corr. Yield,                    __________________________________________________________________________                                                  %                               VIII                                                                             CH.sub.2CHCH.sub.2 NH.sub.2                                                                Sodium Carbonate                                                                        N-allyl O-[1,3-dimethyl-                                                                     --   100 (uncorr.)                                             3-(t-butylperoxy)butyl]                                                       carbamate                                           IX (CH.sub.3).sub.3 CNH.sub.2                                                                 Triethylamine                                                                           N-t-butyl O-[1,3, dimethyl-                                                                  --   99.0 (uncorr.)                                            3-(t-butylperoxy)butyl]                                                       carbamate                                           X  (CH.sub.3).sub.3 CCH.sub.2 C(CH.sub.3).sub.2 NH.sub.2                                      Triethylamine                                                                           N-(1,1,3,3-tetramethylbutyl)                                                                 --   90.0 (uncorr.)                                            O-[1,3-dimethyl-3-(t-butyl-                                                   peroxy)butyl]carbamate                              XI                                                                                ##STR11##   Triethylamine                                                                           N-phenyl O-[1,3-dimethyl- 3-(t-butylperoxy)butyl                              ] carbamate    --   48.5 (uncorr.) m.p.                                                           57-61° C.                XII                                                                              C.sub.2 H.sub.5 C(CH.sub.3).sub.2 OH                                                       Triethylamine                                                                           t-amyl 1,3-dimethyl-3-                                                                       --   87.0 (uncorr.)                                            (t-butylperoxy)butyl                                                          carbonate                                           __________________________________________________________________________     .sup.1 Each of Reactants in Table A was reacted with                          1,3dimethyl-3-(t-butylperoxy)butyl chloroformate.                        

It is noted that certain of the prior art peroxide compounds, used asreactants in the Examples, are disclosed and prepared in U.S. Pat. No.3,671,651 issued to O. L. Mageli and A. J. D'Angelo.

ILLUSTRATION

The following tables show comparative tests run on vulcanizedcompositions of the invention and prior art.

The components of the exemplary formulations, whether ethylene-propylenerubber (EPR), polyurethane rubber, of polyethylene, were milled to anintimate plastic mixture or a standard roll mill such as used in therubber industry. The temperature of the mix during milling was heldbelow 250° F. Under these conditions no scorching occurred in anyembodiment.

The intimately mixed vulcanizable mass was removed from the roll milland a portion placed in a mold and heat cured in a hydraulic press. Thestandard curing time was about 20-30 minutes at 320° F.; othertemperatures and times may be used too. Higher temperatures requireshorter cure times.

Immediately upon removal from the curing press, the cured slabs arepermitted to mature at room temperature for about 24 hours. This timewas sufficient to give reproducible results from control compositions.

For EPR and polyurethane rubber formulations, the matured slabs were cutinto dumbell shaped specimens and tested for tensile strength on anInstron Tensile Tester following ASTM procedure in D412-61T, "TensionTesting of Vulcanized Rubber".

For polyethylene formulations an inch square portion, about 1 gram inweight, was cut from the cured slab and used to determine the percent ofcrosslinking extracting the slab in xylene at 80° C. for 24 hours. Notethat other well known solvent extraction procedures could have beenused. The percent of crosslinking, reported in Table II, represents thepercent of insolubles not extracted from the slab.

                  TABLE I                                                         ______________________________________                                        CROSSLINKING EPR                                                              FORMULATION       INVENTION   PRIOR ART                                       ______________________________________                                        EPR 404 (parts by weight)                                                                       100         100                                             SRF BLACK (PHR)   60          60                                              Sulfur (PHR)      .33         .33                                             1,3-Dimethyl-3-(t-butylperoxy)                                                butyl N-methylcarbamate                                                       (moles of peroxide)                                                                             .015        --                                              1,3-Dimethyl-3-(t-butylperoxy)                                                butyl alcohol (moles of peroxide)                                                               --          .015                                            Cure temp. °F./time                                                                      320° F. for 30 min.                                  Shore hardness    55          55                                              % Compression set 10          14                                              300% Modulus, psi 1485        1020                                            Ultimate tensile, psi                                                                           2135        2140                                            % Elongation      400         595                                             Cure temp. °F./time                                                                      320° F. for 45 min.                                  Shore hardness    55          54                                              % Compression set 9           11                                              300% Modulus, psi 1540        1155                                            Ultimate tensile, psi                                                                           2155        2265                                            % Elongation      400         560                                             ______________________________________                                    

In comparative Table I the EPR polymeric compound formulations were anethylene-propylene rubber, EPR404, sold by Enjay Chemical Company andhad about a 43:57 ethylene:propylene content, a specific gravity of0.86, a Mooney Viscosity. 8 Ml/212° F. of 40, and an ash content of 0.2weight percent. No oil extender was present in these formulations. Acarbon black reinforcing material (Semi Reinforcing Furnace black-SRF)was present and sulfur was used as a coagent. The only difference in theformulations of the invention and the prior art was in the liquid peroxycrosslinking agent, the novel peroxy carbamate compound of the inventionversus the peroxy alcohol of the prior art. In these formulations nocarrier was present.

Crosslinking efficiency is measured by a high Modulus, a low elongationand a low compression set. The two cures in Table I clearly show thatformulation of the invention, in equilmolar concentration in EPR withthe prior art's formulation, gives better crosslinking than the priorart because in both cures the compression set and elongation weresignificantly lower than the prior art's and the Modulus significantlyhigher. These comparative tests show that formulation of the inventionusing the novel peroxy carbamate compound cured to a greatercrosslinking density than the peroxy alcohol of the prior art.

                  TABLE II                                                        ______________________________________                                        Crosslinking of Polyethylene                                                  (DYNH-1-100 PHR)                                                              Peroxide                                                                      ______________________________________                                        1,3-Dimethyl-3-(t-butylperoxy)butyl n-butyl carbonate (C-I)                   1,3-Dimethyl-3-(t-butylperoxy)butyl N-methylcarbamate (C-III)                 1,3-Dimethyl-3-(t-butylperoxy)butyl N,N-dimethylcarbamate                       (C-IV)                                                                      1,3-Dimethyl-3-(t-butylperoxy)butyl alcohol (R-2)                             moles (equivalents of peroxide)                                               C-I         --     --     0.01 0.013                                                                              --   --   --                              C-III       0.01   0.015  --   --   --   --   --                              C-IV        --     --     --   --   0.015                                                                              --   --                              R-2         --     --     --   --   --   0.01 0.015                           Cure Temperature                                                                          320° F. for 30 min.                                        % Crosslinking*                                                                           84.8   86.6   83.3 84.9 81.7 75.2 79.6                            Cure Temperature                                                                          340° F. for 30 min.                                        % Crosslinking                                                                            85.5   89.1   87.6 89.0 84.6 74.4 78.8                            Cure Temperature                                                                          375° F. for 30 min.                                        % Crosslinking                                                                            85.1   88.2   87.1 89.0 84.4 69.2 76.1                            ______________________________________                                         *By solvent Extraction in Xylene at 80° C. for 24 hours.          

The polyethylene used in the examples of TABLE II was a commercial lowdensity polymer with 0.918 density of 2.0 melt index. (DYNH-1 BakelitePolyethylene-marketed by Union Carbide Corp.)

TABLE II shows at equimolar concentrations of the peroxy compounds inthe polyethylene formulations that the C-III peroxy carbamate compoundformulation is about as efficient as the C-I peroxy carbonateformulation and significantly more efficient than the R-2 peroxy alcoholcompound formulation as a crosslinking agent. The C-IV peroxy carbamatecompound formulation is also more efficient than the R-2 formulation.

                  TABLE III                                                       ______________________________________                                        Crosslinking Polyurethane Rubber                                              ______________________________________                                        Formulation                                                                   Genthane S    100    parts                                                    High Abrasion Furnace                                                                       25     PHR                                                      (HAF)Carbon black                                                             Stearic acid  0.2    PHR                                                      Peroxide      moles (equivalent of peroxide)                                  C-III         0.010     0.015   --    --                                      R-2           --        --      0.010 0.015                                   Cure Temperature                                                                            320° F. for 30 min.                                      Shore hardness                                                                              62        67      55    53                                      % Compression Set                                                                           11        5       30    17.5                                    300% Modulus  2165      3690    880   1138                                    Ultimate Tensile                                                                            5665      3690    4820  4267                                    % Elongation  500       240     710   617                                     Cure Temperature                                                                            320° F. for 45 min.                                      Shore hardness                                                                              62        66      55    --                                      % Compression Set                                                                           8         6       30    --                                      300% Modulus  2220      3990    845   --                                      Ultimate Tensile                                                                            5190      4503    4385  --                                      % Elongation  490       333     775   --                                      ______________________________________                                    

The polyurethane rubber, used in the formulations of TABLE III, was acommercial product of the General Tire and Rubber Company marketed asGenthane®-S with a Specific Gravity of 1.19 and a Mooney Viscosity (ML-4(212° F.) of 50±10. This material contained 0.2 PHR stearic acid whichwas added as a lubricant.

Again the comparative TABLE III demonstrates the superior crosslinkingefficiency of the formulation of the invention using a novel compoundover the prior art peroxy alcohol formulation. This superiorcrosslinking is shown by the much lower compression set and elongationand the much higher Modulus.

CURING POLYESTER RESIN BLEND

Two compounds, C-II and C-V, were used as curing agents for astyrene-polyester resin blend in the amount of 1% by weight of agent per100 parts by weight of blend. The blend was prepared by mixing 7 partsby weight of resin and 3 parts by weight of styrene monomer. The resinwas the polycondensate of 1.0 mole of maleic anhydride, 1.0 mole ofphthalic anhydride and 2.2 moles of propylene glycol; the polyesterresin had an acid No. of 45-50.

The S.P.I. gel times, cure times and exotherms were determined (S.P.I.)procedure for running exotherm curves--polyester resins, ModernPlastics, 39, pp. 147 ff. August 1962.) These tests were run at 100 C.The results are set out below.

    ______________________________________                                        Compounds        C-II        C-V                                              ______________________________________                                        Gel Time, min.   4.5         15.7                                             Cure time, min.  6.2         28.2                                             Peak Exotherm, F.                                                                              420         318                                              ______________________________________                                    

The above data indicates that C-II is a medium temperature peroxideinitiator or curing agent while C-V is a higher temperature initiator.

The above working examples are illustrative only and do not limit thescope of the invention, which is as set forth in the description herein.However, these working examples establish that the defined peroxycompounds are safe, efficient and outstandingly effective vulcanizingagents.

Thus having described the invention what is claimed is:
 1. In avulcanizable composition comprising an intimate mixture of a polymericcompound capable of being crosslinked to form a thermoset material and acrosslinking agent in an amount sufficient to afford the desired degreeof crosslinking, the improvement comprising using as said agent a peroxycompound of the formula: ##STR12## where: (a) R₁ is hydrogen or an alkylof 1-4 carbons;(b) R₂ and R₃ are an alkyl of 1-4 carbons; (c) R₄ ist-alkyl of 4-10 carbons, t-aralkyl of 9-16 carbons, t-cycloalkyl of 6-12carbons or ##STR13## (d) Z is ##STR14## (e) R₅ and R₇ are independentlyan alkyl of 1-8 carbons; and (f) D is ethynyl diradical, diethynyldiradical or alkyl diradical having 1-8 carbons.
 2. The composition ofclaim 1 wherein the polymeric compound is selected from the groupconsisting of polyethylene, ethylene-propylene rubber, nitrile rubber,natural rubber, silicone rubber, polyurethane rubber, polyester resin,and ethylene-vinyl acetate copolymer.
 3. The composition of claim 2wherein a filler is present.
 4. A vulcanizable composition whichcomprises an intimate mixture of low density polyethylene and about 1-5PHR of 1,3 dimethyl-3-(t-butylperoxy)butyl n-butyl carbonate.
 5. Amethod of making a crosslinked material which comprises heat curing thevulcanizable composition of claim 1 for a time sufficient to obtain thedesired degree of crosslinking.